Pregnancy Associated Plasma Protein A (PAPPA)

Last updated 25/07/18

Definition

• Maternal serum test used for Combined First Trimester Screening (Maternal Serum Screening (MSS))

Features

• Complex glycoprotein produced by placenta and decidua
• Functions
• Prevention of maternal immune system recognising fetus
• Angiogenesis
• Matrix mineralisation

Indications

• Pregnancy: Maternal Serum Screening (MSS): Combined First Trimester Screening

Procedure

• Venepuncture: at 9 - 13+6/40

Interpretation

• First Trimester: Low levels < 0.37 MoM (5th percentile)
• May indicate poor placentation
• Downs syndrome
• Trisomy 13 (Patau syndrome)
• Stillbirth
• Preterm birth
• Pre-eclamspia: risk of early onset
• Fetal Growth Restriction (FGR)
• May be associated with Invitro Fertilisation (IVF): false positive
• Very low 0.1-0.2 MoM (<1st percentile): significant risk
• >20% have abnormal Dopplers
• 65% with abnormal Dopplers have adverse pregnancy outcomes

Management

• First Trimester: Low levels < 0.37 MoM (5th percentile)
• Mid trimester ultrasound with uterine artery Doppler
• If low levels associated with early growth restriction risk of adverse outcome significantly increased
• Normal: routine antenatal care
• Normal growth but abnormal Dopplers: refer to obstetrician
• Antenatal visits every 4 weeks until 30 weeks
• Repeat ultrasound at 28-30 weeks
• Abnormal: refer to specialist for high risk pregnancies

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References

South Australia Health. Management of Women with a Low PAPP-A and Normal Chromosomes. 19/04/2016